Propellent powder



Patented Nov. 30, 1943 I UNITED STATES 2,335,804 rRorELmN'c rownn'n.

,Charles Earnest Silk, Alton, IlL, ,assignor to Western Cartridge Company, East Alton, Ill.,

a corporation of Delaware r No Drawing.

Application September 21, 1940, Serial No.357,753

- 8 Claims. (01. 52-43) This inv ntion relates to propellent powders, and more particularly to progressive-burning smokeless powders characterized by surface treatment with new and improved deterrent materials.

It has been known in the art of propellent 2,4,5 trimethyl for use as smokeless powderdeterrents, suchas f aromatic nitrohydrocarbons, dialkyl phthalates;

-dialkyldiarylureas, and a "variety Despite the'many proposals which have been made in this art, improvements have been desirable in several aspects, notably in providing deterrent materials which may easily be applied as a coa ing on .powder grains without undesirable agglomer tion of the grains, which result in ballistically as well as chemically stable grains, and which act with greater efiiciency.

It is therefore an object of this invention to provide improved progressive-burning smokeless powder grains.

Another object surface-treated smokeless powder grains having -a desirable combination of ignitibility,-reduced initial combustion rate, appropriate density, and ballistic bility. p Other ob'ects will 'appe'a from the following detaildescripticnr r In accordance. with this invention, "generally stated, the foregoing objects are accomplished by employing a diaryl 'phthalate as tlie surfacesuitable for use in the surface-treatment of powder grains in accordance with this invention, (the approximate melting points in degrees C. being indicated in parentheses) are: diphenyl (73), di-p-cresyl (84), di-o-cresyl (110); di

phenyl (119), and di-a-naphthyl (155) phthalates. V

The ,foregoing and other like esters may be applied as the deterrent coating on singleor multiple-base powder grains of the desired shape and size in accordance with any suitable method. The preformed grains of smokeless powder may be composed of nitrocellulose or other gelatinizable nitrated carbohydrate smokeless powder base, for example nitrostarch, alone or in coinbination, and, if desired, may contain in addition one or more 'nitrated polyhydric alcohols, for example, nitroglycerin; nitroglycol, and the like and/or an aromatic nitrohy ocarhon such as dior trinitrotoluene. The may advantageously be effected as described in the following specific examples, in which detailed directions are suppliedin order fully to illustrate of this'invention is to provide gelatin, or the like, and the emulsion added to treating agent for smokeless powder grains. This *class -of phthalateesters has been found to possess particularly advantageous properties for such use. The solvent and plasticizing properties are conducive to rapid absorption 'at :the surface of the smokeless powder grains and theresulting prodextreme insoiubility in water, the novel deterrents enhance the water. resistance ,pr the treated powde'r grains. v i

; Representative diaryl phthalates, which are the invention.

In one method, the grains may be surface treated while suspended by means of vigorous agitation in an excess of a non-solvent liquid. For-example, the smokeless powder grains may be vigorously agitated in about siX times their weight of water, at a temperature ofabout 0., contained in suitable jacketed-vessel. The diaryl phthalate may be emulsified in a separate vessel in ten to fifteen timesj'its weight of hot water containing about 0.1% Y (based'on the weight of ester) of gum arabic or other suitable protective colloid such as starch, methyl cellulose,

- coating, the grains may be maintained at an elevated temperature at 50 C., with or without agitation, for an additional period up to about 24 hours; The suspen on is then cooled during agitation, the excess quid removed by filtration e or centrifuging, and ,the grainswashed with}; .50.

water. The product may then be dried, asby treatment with warm air heatedto-t50" C. for several days. 'graphited-brought to equilibrium with the desired relative humidity, and ready for. use.

. In accordanc with urface-treatment another well-known be employed when necessary.

of coating process, the treatment may b carried out in a sweetie barrel, consisting of a rotatable cylinder partly immersed in a te p controlling bath or provided with other suitable means for heating and cooling the contents. The powder grains, containing from about one fourth to one half their weight of water, are

placed within the treating cylinder, which is then rotated while the temperature is raised. When the grains have become heated to a temperature of about 70'C.,"'the diaryl phthalate is added, rotation of the treating cylinder being continued. This rotation andiie consequent agitation and mixing of the grains is maintained fora period of about minutes after the addition of the deterrent has'been completed. The mixture is then cooled to room temperature by continuing the rotation while cold water is circulated through the temperature-controlling bath. If additional heat treatment of the grain is desired, the grains may be maintained submerged under hot water in a suitable vessel for the required period. After removal of the excess water by filtering or centrifuging, the product maybe dried, graphited, brought to equilibrium at the desired relative humidity, and stored ready for use.

Aryl phthala'tes which are characterized by a melting point between 60 C. and about 100 C. may be applied in accordance with the above procedures, since the treatment, of the powder grains can then be carried out at a convenient temperature, somewhat above the melting point of the particular deterrent employed. However,

aryl phthalates having melting points above 100 C. may also be utilized in the surface treatment ,of powder grains at convenient temperatures substantially below 100 C. (that is, at temperatures at which the deterrents themselves are solid) either by employing them in admixtures which are. liquid at the desired temperature, or by applying the-deterrent in the form of a solution in a suitable solvent. 7

Where a solvent is thus employed, it should be sufficient in amount to'render the deterrent substance liquid at the temperature of the treatment and should be sufficiently volatile so as to be readily removed from the powder grains during the subsequent drying treatment. Preferably, a solvent is employed for the deterrent which is not a solvent fer the smokeless powder base, for example, aromatic hydrocarbons such as benzene or toluene, chlorinated hydrocarbons such as ethylene dichloride, trichloroethylene, or carbon tetrachloride, alcohols such as ethyl or isoprp pyl, or a solvent naphtha of suitable volatility. However, it may be advantageous at times, in orderto facilitate the coating treatment and/or secure greater penetration into .the powder grains to add to the deterrent solution a volatile solvent for the powder grains, for example, low boiling esters or ketones such as ethyl tor isopropyl acetate, acetone, or ethyl methyl keone.

The amount of deterrent employed may vary in accordance with the type of base powder being treated and the ballistic characteristics desired.

-In general, however, an amount between /2 and about 5% by weight of the powder grains will base powder coated in identical manner in accordance with the first specific example described above, (a) with-diphenyl phthalate exemplifying the new and improved deterrent substances, and

Y (b) with symmetrical diethyldiphenylurea, exemplifying one of the most extensively used deterrents of the prior art. The base powder employed consisted of gelatinized spherical grains, as described in U. SjPate'nt 2,027,114, consisting of nitrocellulose, 2% incorporated dinitrotoluene and 5% nitroglycerin, having a gravimetric density of "0.84 and average grain diameter of 0.019 inch. The deterrent coating amounted in each case to 5% by weight of the powder. The

resulting powders,. having gravimetric densities of (a) 0.86 and (b) 0.84, were loaded and fired in .30 caliber-1906 ammunition having a bullet weighing 150 grains. In this ammunition, a. 36.8 grain charge of theuncoated powder' roduced a muzzle velocity of 2470 feet per second at a pressure of 45,000 pounds per sq. in. The comparative test data are listed in the following table:

The diaryl phthalate deterrent in accordance.

with this invention displayed superior results particularly with respect to efficiency (a smaller charge of the powder treated therewith being required to provide the desired ballistics) and in the ignitibility of the coated powder (shown by smaller changes in the ballistic properties on lowering the firing temperature from about 25 C. to 40 C.).

Microscopic examination of thin sections of grains of the diphenyl-phthalate-coated powder revealed the presence of a uniform surface layer in which the novel deterrent was concentrated.

Similar, study of the grains after storage of the powder at 50 C. for 30 days showed that no appreciable alteration of this structure had occurred.

' Firing tests carried out afterthis period of storage at 50 C. likewise substantiated the ab sence of any significant change in the ballistic provide the desired results, it being understood however, that somewhat higher proportions may As illustrative of the advantages which? may be secured by use of the deterrents in accordance with this invention, the following table contains ballistic test data obtained with a given properties of diaryl-phthalate-coated powdergrains on being subjected to elevated temperatures, this result representing a considerable improvement over liquid ester'deterrents such as diethyl phtha late heretofore in use.

It will be understood that the invention is not to be limited to thespecific' details stated above but that variations may be made, as will be realized by those skilled in the art, which are contemplated within the scope of the following claims.

Having now described the'invention, what'is claimed as new and is desired to be secured by Letters Patentiis:

Multiple-base propellent powder grains surface-treated with dipheny] phthalate.

7. Nitrocellulose-nitrog1ycerin 'propellent powder grains surface-treated with a diaryl phthal- 1. Propellent powder grains surface-treatepl' 5. Multiple-base propellent powder grains surface-treated with a diaryl phthalate.

ate.

8. Nitrocellulose-nitroglycerin propellent powder grains surface-treated with diphenyl phthalate.

CHARLES EARNEST SILK. 

